Federal Models

1. Disconnect the vacuum hose (green stripe) from the throttle body, and connect a vacuum pump to the vacuum hose.





2. Check the above points when the engine coolant temperature is 50° C (122° F) or below (cold) and when engine coolant temperature is 8O - 95° C (176 - 205° F) or higher (warm).

Vacuum Source Inspection

NOTE: Verify that engine coolant temperature is 80 - 95° C (176 - 205° F).

1. Disconnect the vacuum hose from the throttle body exhaust gas recirculation vacuum nipple and connect a hand vacuum pump to the nipple.
2. Start the engine and check to see that, after raising the engine speed by racing the engine, E port vacuum rises proportionately with the rise in engine speed. If there is a problem with the change in vacuum, it is possible that the throttle body E port may be clogged and require cleaning.